This application is based on application No. 99-28990 filed in the Korean Industrial Property Office on Jul. 16, 1999, the content of which is incorporated hereinto by reference.
(a) Field of the Invention
The present invention relates to a low-voltage blue color fluorescent substance and a manufacturing method of the same, more particularly, to a luminance improved low-voltage blue color fluorescent substance for a Field Emission Display (FED) or a Vacuum Fluorescent Display (VFD), and a manufacturing method of the same.
(b) Description of the Related Art
Low-voltage displays rated at one kilo volt (kV) or less mainly include Field Emission Displays (FED), Vacuum Fluorescent Displays (VFD), etc. The Field Emission Display is actively being studied as a next generation small sized Flat Panel Display (FPD) component, and the Vacuum Fluorescent Display (VFD) is mainly being used as a variety of display components for household electric appliances, audios and videos (AV), automobiles, etc. These low-voltage display panels are constructed so that electrons emitted from an electron emitter such as a heating wire irradiate fluorescent substances resulting in the production of desired images.
Fluorescent substances for low-voltage driven device such as Field Emission Displays, Vacuum Fluorescent Displays, etc. should have low electrical resistance, low luminescence initiating voltages, high luminescence efficiency, no luminance saturation, minimal defects on the fluorescent substance particle surface, stable low-velocity electron excitation luminescence conditions, and do not undergo decomposition. Currently, a sulfide based fluorescent substance is widely used as a fluorescent substance for low-voltage driven device. As the host materials of sulfide based fluorescent substances have high resistance, conductive materials are added to these substances so that they can be used in low-velocity electron-beam excitation applications. However, non-sulfide based fluorescent substances are actively being developed as there are problems of oxide filament contamination and fluorescent substance efficiency deterioration due to sulfide based gas emission and fluorescent substance material decomposition scattering during electron-beam excitation.
ZnGa2O4 is a notable fluorescent substance as it has relatively superior luminance and exhibits a stable blue color. ZnGa2O4, as a complex oxide of ZnO and Ga2O3, has an optical band gap of about 4.4 electron volt (eV). During electron-beam excitation, the electron does not directly excite the center of the fluorescent material, but first excites the host material of the fluorescent material and this energy is transferred to the center of the fluorescent material to cause luminescence.
A low-voltage blue color fluorescent substance is manufactured through a process comprising the steps of mixing raw materials with flux; performing a primary burn; ball-milling and washing; and the performing of a secondary burn and classification. Flux can be added to increase particle diameter during the burning. It is known that even though flux needs to be added in order to improve luminance of sulfide based fluorescent substances, luminance rather deteriorates when using flux with other fluorescent substances. Additionally, U.S. Pat. No. 5,478,499 discloses the blue colored fluorescent material ZnO Ga2O3 that is luminescent below 100V and which is doped with 800 to 2,300 parts per million (ppm) of lithium (Li) and 100 ppm of phosphorous (P) or less. However, the degree of luminance improvement of this disclosure is minute.
It is an object of the present invention to provide a low-voltage blue color fluorescent substance having an excellent luminance improvement effect and a manufacturing method of the same by including an appropriate amount of P on the fluorescent substance""s surface.
In order to accomplish the above object, the present invention is manufactured so that the amount of P in a fluorescent substance composed of zinc oxide and gallium oxide should amount to 0.5 to 3 weight %.